Metal deforming percussion tool



March 5, 1957 A. A. HUTCHINS METAL DEFORMING PERCUSSION TOOL Filed Feb. 12, 1953 United States This invention relates to improved portable percussion tools of a type particularly adapted for use in hammering out irregularities in sheet metal or the like, as for instance in removing dents from automobile bodies.

The usual way of straightening dents in an automobile body or fender is to hammer outwardly against the underside of the dent until the metal is returned to its original smooth shape. One difficulty heretofore encountered in such work has resulted from the inaccessibility of the underside of the body at certain points, as for example at the underside of the fenders near the wheels, which inaccessibility has customarily necessitated partial disassembly of a wheel or other part of the auto atent O i shown in Fig. 1 as it is held in the hand of a user.

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action by a spring and detent mechanism whose details will be discussed at a later point.

The above and other features and objects of the present invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawing, in which:

Fig. 1 is a perspective view of a device embodying the invention;

Fig. 2 is an enlarged section through the Fig. 1 device;

Fig. 3 is a fragmentary section taken on line 33 of Fig. 2;

Fig. 4 is a view taken along line 44 of Fig. 3; and

Fig. 5 is a fragmentary partially sectional side View of the device showing an attachment or extension connected to the main body of the device.

A pneumatic hammer 10 embodying the invention is As is apparent from that figure, the device includes a body 11, which is held against the palm of the operators hand, and which carries a hammer element 12 adapted to be actuated outwardly away from the operators hand. Actuation of the hammer element 12 is controlled by an axially movable push button type control element 13, which is engageable and inwardly movable by the operators thumb. Compressed air or other actuating fluid is supplied to the device through a flexible hose 14. As seen in Fig. 2, hammer element 12 is carried and actuated mobile before a hammer blow could be applied at a desired location. Also, at some locations where the body surface is curved or cavitated relatively sharply, it may be very difficult to apply a hammer blow without striking unintended portions of the body.

A major object of the present invention is to provide an improved power operated percussion tool which is adapted to be held in the hand of an operator, and is so designed as to be movable into and operable within restricted areas which are not normally accessible. More specifically, the device includes a body which may be held against the palm of an operators hand, and which carries a power actuated preferably pneumatic hammer element at a side of the body facing away from the operators hand. In order to permit accommodation of the device in a restricted area, the body is preferably so shaped that its maximum dimension in the directionof hammer movement is at least as small as its maximum dimension transversely of that direction of movement. To facilitate operation of the tool, the energization of the hammer is desirably controlled by a manual control element, typically a valve actuating handle which is movably carried by the body. This control element may be positioned for actuation by a thumb or finger of the operator, and for that purpose is desirably movable transversely of the axis of hammer movement.

To permit projection of the hammer into a recess in an automobile body, the body of the tool may be ex-' ternally tapered about and toward the hammer element. Also, I contemplate providing an attachment for use with the tool and comprising a flexible elongated hammer carrying unit extending from the tool body and adapted for insertion into certain types of narrow areas for which the tool itself is not designed.

The hammer is desirably actuated by a piston mounted in a bore in the body and operated by a pressure fluid, preferably compressed air. The flow of air or other fluid to the piston may be controlled by the previously mentioned control element, through a control valve, which may be of the snap action type to assure a fast striking action by the hammer. The valve may be given its snap by a piston 15, which is movable within a cylinder bore 16 in the body. The admission of air to cylinder 16 is controlled by a snap action valve assembly 17 actuated by element 13 and contained within rear chamber 18 in the body.

The body 11 of the device includes a main section 110, a rear cover section 11b closing the rear side of valve chamber 18, and a forward section which partially closes the forward end of cylinder bore 16. The rear cover 11b and forward body section 116 may be attached to main body section 11a by a number of circularly spaced screws 20 and 21. The maximum overall dimension of these three body sections in the direction of the piston axis a is preferably at least as small as, and for best handling smaller than, the maximum dimension of the body transversely of the axis. An annular gasket 22 may be provided between sections 11a and 11b to prevent the leakage of actuating fluid from valve chamber 18. g A rear portion of main body section 11a has a cylindrical outer surface 19, of a diameter corresponding to the diameter of cover 11b. Forwardly of surface 19, body section 11a presents a frusto-conical outer surface 23, which tapers forwardly and toward hammer element 12. Cylindrical surface 19 and fmsto-conical'surface 23 are centered about the axis of piston 15 and hammer element 12. The rear planar surface 24 of rear cover 11b, which surface engages the palm of a users hand, preferably extends directly transversely of the axis of the piston and hammer element.

Forward section 110 of the body has a mounting flange 25, beyond which it presents an outer frusto-conical surface 26, which is centered about the piston and hammer axis and tapers forwardly and toward that axis. Body section 110 contains a cylindrical bore 27, extending axi ally of the piston, and within which the externally cylindrical hammer element 12. is received. Preferably, the diameter of bore 27 is somewhat larger than the external diameter of hammer element 12, to allow the escape of line positions of Fig. 2. As will be understood, hammer element 12 is rigidly attached to and projects axially from piston 15. The hammer element may have at its outer end a small diameter central projection 30, which engages and acts against a work piece upon outward actuation of the element.

Piston I is actuated to the left by air introduced into cylinder 16 through passage 31 at the right end of the cylinder. After a leftward actuation of the piston, the air within the right end of the cylinder is allowed to esc'apethr'oug'h a small bleed passage 32 extending through the piston. This passage isof a size (typically about .022") sufficiently small to assure actuation of the piston upon initial introduction of air into the cylinder through passage 31, while at the same time permitting a fairly rapid escape of the air after passage 31 is closed. For thispurpose,bleedpassage 32 must of course be considerably more restricted than inlet passage 31. The air which bleeds through passage 32 after an actuation of piston flows along the clearance space between hammer element 12 and bore 27, and is thus vented to the atmosphere. Such passage of air between the hammer element and its guiding bore cleans out the space between these-parts in a manner preventing the acc'umulationof dirt or dust in the device.

Control'eleme'nt 13 has an elongated stem 33 which extends and is axially'mova'ble within a bore 34 formed in the wall of body section 11a. This stern moves directly transversely of the axis of piston 15 and hammer element 12, and moves along an axis which intersects the'piston axis. 'Stem 33 carries at its outer end apu'sh button head which is'engaged by the operators thumb, and is yieldingly urged outwardly by coil spring 35. Air leakage from within chamber 18 along the stem of element 13 is prevented by packing 36.

Thesnap action valve mechanism 17 includes a sliding valve disc 37, having a planar surface engagihg'a corresponding planar wall 42 of chamber 18, 'an'd'which is slidable along the wall between the full line and broken line positions of Fig. 3. In the full line position of Fig. 3, valve disc 37 closes passage 31 to prevent the admission of air into cylinder bore 16 from valve chamber 18. In its broken line position, valve disc 37 opens passage 31 to admit compressed air to the cylinder for actuating piston '15 and hammer element 12. The air is admitted to valve chamber 18 through a passage 33, which extends transverselyof the piston axis and connects through a transverse tubular fitting 138 with supply hose 14.

Valve disc 37 is carried and actuated by a swinging arm 39, which comprises an elongated sheet metal element containing an opening through which a stem projecting from disc 37 extends. Arm 39 is mounted for swinging movement about a pivot pin 41. The sheet metal "forming arm 39 extends in close proximity to wall 42 of valve chamber 18, and at its mounting end is deflected outwardly away from that Wall at 43, and then back at 44 toward the opposite end of the arm. Mounting pin 41 extends through the metal of arm 39 both at a location directly'adjacent chamber wall 42, and at its outer portion 44, to thus very effectively mount the arm for its desired swinging movement. Outer porion 44 of arm 39 is preferably curved outwardly as shown, to slidablyengage cover 24 and thus retain the arm and disc against chamber wall 42.

Aetuating force is transmitted from thumb pressed element 13 to valve carrying arm 39 by a wire spring 46, which extends at one end through the inner portion of element 13, and at the other end is looped about the stem of a headed pin or screw 47 carried at the swinging end of arm 39. In the normal full line position of Fig. 3, spring 46 is under some compression, and tends to yieldingly urge arm 39 towardits broken line position. However, actual movement of the arm toward that broken line position is normally prevented by a retaining detent element 48, which continues to prevent suchmovement of arm 39 even after a user has commenced to press element 13 inwardly. Upon inward actuation of element 13, the initial movement of the element acts to progressively increase the compression of spring 14 and thus increase the force tending to urge arm 39 to its valve opening position, until ultimately detent 48 is released (in a manner later to be brought out) and permits the arm to snap rapidly to its valve opening position under the influence of the spring.

The detent for releasably retaining arm 39 in its full line Fig. 3 position comprises a swinging rigid sheet metal arm 48, which is pivoted about a pin 49 for movement between its full and broken line positions of Fig. 3. At its end, detent 48 is deflected outwardly to present a shoulder 50, against which an upstanding car 51 of arm 39 abuts. Such engagement of ear 51 with detent shoulder 50 retains arm 39 against valve opening movement until detent 48 is deflected to its broken line position. The detent is yieldingly urged toward its full line active position by a spring 52. For releasing the detent after predetermined inward movement of actuating element 13, spring 46 has at its end a portion 53 which is curved toward the detent member. Inward movement of element 13 causes the portion of spring 46 which engages pin 47 to swing about that pin in a manner ultimately actuating end 53 of the spring against detent member 48, and thereby deflecting the detent member to its inactive broken line position, and thus releasing arm 39 for snap movement to its open broken line position.

In using the device of Figs. 1 to 3, an operator holds body 11 against the palm of his hand as shown in Fig. 1, and then positions the device so that hammer element 12 is opposite a car body dent to be straightened. The users thumb then presses actuating element 13 inwardly to open valve element 37 with a snap action, in a manner suddenly admitting a charge of compressed air to cylinder 16. This air actuates piston 15 in a manner causing hammer element 12 to strike against the work. Release of actuating element 13 closes the air passage 31 to cylinder 16, so that spring 29 may retract the piston andhammer element to their full line Fig. 2 positions, while the air is permitted to bleed from the cylinder through bleed passage 32 and the space between the hammer element and its guiding bore 27.

Because the overall dimension of the tool body 11a, 11b and 11c in the direction of the piston axis is -at least as small as, and preferably smaller than, the dimension or diameter of the body transversely of that axis, the user may rather easily move his hand and the device into a restricted area which would not receive prior pneumatic hand tools. For example, the users hand and the device may be moved into the space between an automobile tire and an adjacent fender, to permit hammering of the dented portion of the fender outwardly without necessitating removal of the wheel. The formation of body sections and 110 to taper forwardly toward and about hammer element 12 permits the portion of the body about the hammer element to be moved into depressions or cavities, which might otherwise be inaccessible. With the device in a position opposite the dent which is to be straightened, the user merely actuates control element 13 enough times to exactly straighten the dented metal.

Fig. 5 shows the device 19 with an attachment or extension 54 connected to it, the attachment being intended to adapt the device for use in certain types of restricted areas which may be shaped somewhat diflerently than the areas for which the tool in its Fig. 1 condition is especially adapted. This attachment includes a flexible rubber hose 55 which is threadedly connected at one end to an attaching member56, which member is substituted for forward body section 11c of the device to placehose 55 in communication-with cylinder bore 16. In using attachmeat 54, -'the-piston 15, hammer element 12, and spring 29 are removed from bore 16. Hose 55 is threadedly connected at its outer end to a two-section cylinder 57, which contains a piston 58 carrying a hammer element 59. Piston 58 is urged in a retracted direction by spring 60. The outer surface of cylinder 57 about hammer element 59 tapers at 61 toward the opening 62 through which the hammer element is projectible. Surface 61 may taper more abruptly at one side than at the other, as shown, to permit the hammer to be positioned and operated in very inaccessible locations. In using the extension of Fig. 5, an operators holds "body and actuates element 13 with his thumb to introduce surges of air into cylinder bore 16. Each such surge of air flows through hose 55 to actuate piston 53 and hammer 59 in the same manner that piston 15 and hammer 12 have been described as operatmg.

Piston 58 of course contains the same bleed passage corresponding to that shown at 32 in Fig. 2, and hammer element 59 is spaced from the bore through which it passes, to allow escape of the air after each operation. The provision of such a small cylinder at the outer end of a flexible hose permits positioning of the hammer in some locations which are inaccessible to the body 10.

I claim:

1. A portable percussion tool comprising a body adapted to be held in the hand of a user and containing a cylinder bore, a piston reciprocable within said bore, a. movable valve element operable to admit piston actuating fluid to said bore, a movable manual actuating element operable by a finger of the user, snap action means pivoting said valve element in response to movement of said actuating element and at a speed greater than the speed of movement of the actuating element, and a tool reciprocable by said piston and projecting from a side of said body.

2. A portable percussion tool as defined in claim 1, in which said snap action means is located within a chamber in said body and comprises a spring for yieldingly transmitting actuating force between said actuating element and said valve element, detent means releasably maintaining said valve element against opening movement by the actuating element, and means for releasing said detent means after spring energizing movement of the actuating element.

3. A portable percussion tool as defined in claim 2, in which said valve element comprises a swinging arm, and said detent means comprise a spring urged detent acting against said arm.

4. A portable pneumatic percussion tool adapted to be gripped by the hand of the user comprising a body having a back portion and a front portion, said body having a front to rear dimension less than its transverse dimension, a piston carried in a bore in said body opening toward said front, a short guide member joined to the front portion or said body and covering said bore, said guide member having a much smaller transverse dimension than said body, an impact member carried in a bore in said guide member and joined to said piston for reciprocation therewith, a valve carried in a chamber in said-body for admitting fluid pressure to said piston, and a hand-actuated valve controlling element projecting outwardly from the edge of said body,

References Cited in the file of this patent UNITED STATES PATENTS 208,291 Carr ct al Sept. 24, 1878 286,803 Fletcher Oct. 16, 1883 1,258,206 Fetcher Mar. 5, 1918 1,924,946 Kott Aug. 29, 1933 2,052,975 Griffin Sept. 1, 1936 2,483,626 Daku Oct. 4, 1949 2,490,254 Casazza Dec. 6, 1949 2,526,380 Mathews Oct. 17, 1950 2,534,525 Molloy Dec. 19, 1950 2,594,522 Thompson Apr. 29, 1952 2,646,075 Elkington July 21, 1953 

